U.N. Chief Says Report Will Confirm Gas Massacre

Ban Ki-moon, the United Nations secretary general, said Friday that he believed that an impending report he had commissioned on the massacre of Syrian civilians last month would be “overwhelming” in showing that chemical weapons were used.

In an apparently off-the-cuff response to a question that caught even his press office by surprise, Mr. Ban also said he believed that President Bashar al-Assad of Syria “has committed many crimes against humanity.”

Mr. Ban did not explicitly attribute the Aug. 21 attack to Mr. Assad’s forces, and he has repeatedly asserted that the report on the attack would determine only whether chemical weapons had been used — not who had used them. But his remarks quickly spread via Twitter messages and immediately raised the question of whether he knew or had judged the report’s conclusions before he had seen it.

“I believe that the report will be an overwhelming, overwhelming report” that chemical weapons were used, “even though I cannot publicly say at this time before I receive this report,” Mr. Ban said at a women’s forum at the United Nations headquarters, which was captured on an internal video broadcast.

Farhan Haq, Mr. Ban’s spokesman, told reporters later at a regular midday briefing that Mr. Ban did not have the report and that “he has not made up his mind on a report that he has not yet received.”

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As thousands of Syrians flee the war every day, many have become indefinitely separated from their families and from a country that is increasingly becoming divided and unstable.

Mr. Ban’s remarks came as the lead scientist of the chemical weapons inspection team that composed the report said it had been completed and would be delivered to Mr. Ban soon. The scientist, Ake Sellstrom, a chemical weapons expert from Sweden, was quoted as telling The Associated Press in a telephone interview from the Netherlands, “It’s done, but when to present it is up to the secretary general.”

Diplomats and arms control experts have said that they expect the report to be conveyed to Mr. Ban by Monday and perhaps earlier, and that they expect it to give ample proof that chemical munitions were deployed. Mr. Ban has said he would promptly share the report’s findings with all 193 United Nations member states.

Mr. Haq said, “As of right now, we still don’t have a day for when the report will be presented.”

Pressed about why Mr. Ban made such remarks, Mr. Haq said, “I’m not privy to the information he has.”

The United States, Britain and France have all concluded already that chemical weapons were used in the Aug. 21 attack, and they have accused Mr. Assad’s forces of responsibility. Mr. Assad and Russia, his principal ally, have asserted that the insurgents seeking Mr. Assad’s demise were culpable. But all parties in the Syrian conflict still regard the report as important because it will provide the first independent assessment of the attack itself.

A number of United Nations diplomats and arms control experts have said they expect that the evidence presented in the report will implicate Mr. Assad’s side in the 30-month-old Syrian conflict. Some have said the report could intensify the pressure on Mr. Assad to promptly comply with the international treaty banning chemical weapons, which he formally agreed to join on Thursday in response to what he called the advice of Russia.

In Washington, a State Department spokeswoman, Marie Harf, declined to speculate on whether the report would have a bearing on the diplomatic talks under way in Geneva between Secretary of State John Kerry and Russia’s foreign minister, Sergey V. Lavrov, over a Russian proposal to quarantine and destroy Syria’s chemical weapons stockpiles, or on parallel talks under way among the five permanent members of the Security Council in New York.

“I know there are rumors about it coming out possibly soon,” Ms. Harf said of the report in response to a question at the department’s regular daily briefing. “I think that — I’m confident, actually, that the U.N. report will reaffirm what we’ve long said.”

A version of this article appears in print on , Section A, Page 8 of the New York edition with the headline: U.N. Chief Says Report Will Confirm Gas Massacre. Order Reprints | Today’s Paper | Subscribe